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Thread: Roll cage tube specification thread - MSA & FIA info

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    Banned after significant club disruption Dec 5th 2014 Chris Eyre's Avatar
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    Default Roll cage tube specification thread - MSA & FIA info

    .
    Various are now beginning to construct or modify their roll cages, so here's a bit of a summary to help understand the FIA / MSA minimum specification requirements.

    If you're prepping a track car, one day you might want to sell it, so if you do the cage compliantly, you can put value in a car by ensuring that someone can race it.

    This isn't directed at the many members who just want a car to have fun in, and don't want to take it too seriously. It's just to give out information which isn't exactly readily available unless you know where to dig for it, with established safety reference points it beings (ie the MSA/FIA).

    Comments on this thread are welcome - I initially started writing it last winter and having re-read it today, believe it to be right.

    ---------------------------------------------------------------------------------------------------------

    Minimum specifications

    1) MSA

    The MSA blue book gives these one-size-fits-all minimum specifications for racing (Saloon, Single Seater and Sports Cars).

    This concerns non-MSA certificated/non-FIA approved cages.

    [Does not include rally - I believe rally cages require FIA / approval certificates, though this could again depend on the level.]

    Quote Originally Posted by MSA Blue Book 2011, Section K, p156

    27. Minimum CDS tube specifications are:

    • Minimum Material: Cold Drawn Seamless Carbon Steel
    • Minimum Yield Strength: 350 N/mm2
    • Minimum Dimensions (Ø mm):
    • 45x2.5 or 50x2.0
    • 38x2.5 or 40x2.0 (for roll cages/bars approved prior to 1995)
    (though it further specifies Sports Car roll hoops, but we'll skip that, since this forum is about 'Saloons')

    ** Please note that optional cage member minimum dimensions have been reduced from 2011, noted on p2 of this thread **

    Turn up with this spec, and (subject to proper installation) you are MSA compliant and can use the cage in UK National competition (not International).

    Where a cage is uncertificated, the MSA require an 6mm hole to be drilled into a part of the cage (often the screenrail) where the tube thickness can be quickly seen by a scrutineer, to establish the correct thickness.


    2) FIA

    Subtle differences to MSA, but note that MSA post-1995 minimum exceeds FIA:

    Quote Originally Posted by FIA Appendix J 2009, Article 253, p14

    8.3.3 Material specifications
    Only tubes with a circular section are authorised.

    • Minimum Material: Cold Drawn Seamless Carbon Steel
    • Minimum Yield Strength: 350 N/mm2
    • Minimum Dimensions (Ø mm):
    • 45x2.5 or 50x2.0 (main rollbar or lateral rollbars)
    • 38x2.5 or 40x2.0 (lateral half-rollbars and other parts of the safety cage)
    In the UK, if you run an FIA-certificated cage, which is below MSA minimum CDS spec (1, above), be prepared to be asked for a copy of the FIA cage certificate by a scrutineer.

    Quote Originally Posted by FIA Appendix J, 2009, p14 + MSA Blue Book, 2009, p161
    In selecting the steel, attention must be paid to obtaining good elongation properties and adequate weldability.

    The tubing must be bent by a cold working process and the centreline bend radius
    must be at least three times the tube diameter. If the tubing is ovalised during bending, the ratio of minor to major diameter must be 0.9 or greater.

    ---------------------------------------------------------------------------------------------------------

    Lighter cages

    Lighter cages can be used in either of the following circumstances:

    1. If you have an FIA approved cage, made of thinner diameter CDS or T45 light tube

      or
      .
    2. You have a certified cage (either material), whereby the MSA Tech Dept have signed it off.

    These cages can be either CDS or T45 constructed. Aluminium was outlawed in the late '80s, and must not be used in FIA/MSA competition (scrutineers arm themselves with magnets, so you will get caught) and is generally inadvisable.

    It costs money to get a cage MSA certificated (or FIA approved) so it is financially prohibitive to "just get" a certificated cage fabbed up down your local tube benders. You end up going to a recognised manufacturer of roll cages, who (depending on target use & size of market) may/may not get a cage certificated.

    Turn up with thin-wall / thin dia tubing on a cage which isn't Certificated or FIA approved, and the scrutineers will not allow a car to race, because if anything happens, those scrutineers are running an liabilty risk: it isn't of the minimum uncertificated spec, and it's not rubber stamped; therefore can't be used.

    The whole logic is that that the DIY-er, or one-off cage producers, cannot make inroads into the safety buffer designed into the one-size-fits-all heavier cages given by the MSA or FIA, above.


    ---------------------------------------------------------------------------------------------------------

    Modifying MSA-certificated or FIA-approved cages

    Minefield!

    • Any tube modification to a cage of this type technically removes the MSA / FIA approval it has gained.
    • Welding tags onto tubes to bolt them to A / B pillars is a grey area, but it would be unlucky for this to cause an issue.

      Modifications?
    • An addition of a doubled-up rear diagonal or full X-door bars is enough to render a cage 'uncertificated'/'unnapproved' because the cage no longer matches the approval drawing! (and the same way countless cars are excluded from post-event scrutineering around the world, by virtue of not matching homologation drawings, even if it doesn't make the slightest bit of difference!).
    • If an FIA cage is modified, it can no longer be used International competition
    • For UK racing, it is then a question of whether it complies with the min specification in MSA Blue Book, Section C(c), p161, para 27. But it's MSA / FIA approved for a reason, and may well have a light tube construction.
    • The cage is then reliant on the cooperation of a scrutineer who is prepared to accept it, which is not a foregone conclusion.
    • Whilst it is widely known that there are a lot of modified cages in existence, do not blindly travel to events where you are unsure of those who are officiating: modificatoins could render the cage instantly useless for Saloon racing purposes.



    ---------------------------------------------------------------------------------------------------------


    How do full-on, lightweight cages differ from MSA / FIA minimum CDS specifications, above?

    Roll cage manufacturers work to narrower parameters. Sample FIA T45 cages are then sent to the FIA for testing (edit 5/12) or the local motorsports authority, ie the MSA.

    This is a Subaru Impreza WRC cage, which was assembled independently of any car, solely to send to the FIA in France to gain their approval for future use:



    The recommended construction data is not given out in any FIA rulebooks.

    However, here is a guide to some actual T45 data I have seen from a 'well known' roll cage manufacturer:

    • A-pillars - 45 x 16 guage (1.6129mm)
    • Screen bar - 45 x 1.6mm
    • Door bars - 45 x 16 guage (1.6129mm)
    • Dash bar - 40 x 1.5mm
    • Main hoop - 45 x 16 guage (1.6129mm)
    • Rear stays - 45 x 1mm
    • Rear diagonal - 45 x 1mm

    These are not CDS tube specifications - T45 is thinner.


    Here is another one: Seat Leon works cage. Assume T45 (but it isn't stated):



    This gives some pointers as to where weight savings are made on sophisticated cages. In theory you could attempt to replicate these for a self-build trackday cage which you don't intend to race or a cage you intend to personally stump the cash for to get MSA certified / FIA apprived, but do not copy these blindly - do your own research and make your own decisions.

    Disclaimer:

    You buy or make or install your own roll cages at your own personal and eligibilty risk: not mine, and not Club GTI's.

    References
    MSA Blue Book - Competitors Safety section here
    FIA Appendix J 2009, Article 253 - here


    As before, if this post is copied to other forums, be good and credit www.ClubGTI.com - thanks
    Last edited by Chris Eyre; 3rd June 2011 at 12:16. Reason: MSA reference updated

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    Cheers Chris - This is a great help - the only "issue" I have ever had is about the bolts securing the cage where the "Scrute" decided he knew how to measure the bolts by eyesite alone and told me that they were insufficient imperials and should be 8mm whereas they are actually 6mm with captive nuts !(which could be a real pain if they ever need replacing !)
    Thanks once again

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    Banned after significant club disruption Dec 5th 2014 Chris Eyre's Avatar
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    No problems - I'm glad I've found a use for it, rather than it being theoretical but not used in practice!

    I've just checked: the FIA minimum bolt size, for cage feet, is the same as MSA - M8 / 8mm minimum, of 8.8 grade (MSA detailed in the roll cage installation thread).

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    Chris

    In the blue book is there anything about spaceframe constructions?

    All manner of tubing be it square or round finds its way into spaceframe chassis and just wondering if there are any rules in the blue book.

    Hillclimbs and sprints are pretty much a free for all but mainly wondering about track racing.

    Thank you

    Carl

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    Another question which may fit better in another section....but seems right here...

    At what point of extreme modification does a saloon become a 'special' or something else and therefore the saloon rollcage rules would not apply even if the spaceframing starts around a saloon cage?

    Cheers

    C

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    Is this to do with spaceframing the front end, ie cutting off the inner wings?

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    Chris

    Yes, front end and not using original chassis legs and also the floor to create a flat bottom.

    C

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    Which specific MSA category are you planning on racing it in?

    Cars which have had their inner wings removed have become ineligible, MSA-wise, in the past - eg Polog4tracer commenting ad hoc-ly on his stillborn project here - but I'm not sure where that was intended to be raced.

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    Chris

    If it was the late 70's it would be special saloons

    I think hillclimbs, sprints and anything goes libre type stuff. If it isn't finished before house buying and kids then it will be track days only.

    C

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    Special Saloons... ie cut down saloon bodies, space framed underside etc?



    Baby Bertha etc?

    I guess they're around being accomodated somewhere but can't place where they still exist..

    Struggling to find anything on them in the MSA Competitors Safety section...

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    Thatt's the ticket. Great racing and wild privateer garage engineering. Alot of them still exist and owned by those who drove them. Recently at least 2 or 3 have been restored. There is a long standing thread on the autosport nostalgia forum with lots of pics and info.

    C

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    I had always thought the main hoop and A pillar bars in these T45 cages were still to the msa minimum specs but it seems I am wrong? It would be interesting to see what tube specs have been used in one off T45 cages built by people like protection and performance, or custom cages where they haven't been sent to the FIA for approval?

    For some reason I had always thought that the bars which wern't compulsary therefore you are adding them at your choice could be of any material specs you wanted, as long as the main cage structure as laid out in the blue book is made from the correct thickness and dimaeter.

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    Quote Originally Posted by Hamish
    I had always thought the main hoop and A pillar bars in these T45 cages were still to the msa minimum specs but it seems I am wrong?
    The MSA don't quote T45 specs at all - everything I could find went into post 1 and it all refers to CDS.

    Quote Originally Posted by Hamish
    It would be interesting to see what tube specs have been used in one off T45 cages built by people like protection and performance, or custom cages where they haven't been sent to the FIA for approval?
    This is pukka T45 tube data:

    Quote Originally Posted by Chris Eyre
    The recommended construction data is not given out in any FIA rulebooks.

    However, here is a guide to some actual T45 data I have seen from a 'well known' roll cage manufacturer:

    • A-pillars - 45 x 16 guage (1.6129mm)
    • Screen bar - 45 x 1.6mm
    • Door bars - 45 x 16 guage (1.6129mm)
    • Dash bar - 40 x 1.5mm
    • Main hoop - 45 x 16 guage (1.6129mm)
    • Rear stays - 45 x 1mm
    • Rear diagonal - 45 x 1mm

    These are not CDS tube specifications - T45 is thinner.

    Quote Originally Posted by Hamish
    For some reason I had always thought that the bars which wern't compulsary therefore you are adding them at your choice could be of any material specs you wanted, as long as the main cage structure as laid out in the blue book is made from the correct thickness and dimaeter.
    There is a degree of doubt about this in my mind, but I am only referencing to things I have seen on cars, rather than what I have seen in the rulebooks (off which this thread was written).

    More than happy to explore this further if anyone has extra info to add

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    I am still of the opinion that you can use thinner T45 tube . After all people like custom cages and protection and performance make one off T45 cages which wont have FIA certification and I bet they arn't using proper spec tube throughout!

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    Custom Cages were reluctant to make a T45 Mk1 cage for me a few years back, even using the same drawings as their CDS multipoint kit, saying it wouldn't be admissible for competiton and they'd need me to sign something.

    P&P are much more flexible and certainly did one for Jettadan, and PhatVR6.

    I'd be more than happy to be wrong though - it opens up lightening opportunities for all !

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    I have read and understand the rules in the blue book just as you have, and it states a minimum diameter and wall thickness. However like you say there are some companies using T45 for one off cages and I dont think they are using minimum spec tubing for all of it? Can Paul confirm what spec tubing has been used for all the bars in the corrado?

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    If it's ok with pascal, probably best we lift the cage spec debate posts over to here:

    http://www.clubgti.com/forum/showthread.php?t=202315

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    On the cage tubing spec conversation you can mix different thickness of tubing. The blue book spec's what thickness and where you can use it.

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    I've just split the CDS/T45 debate from pascal's Audi S4 project thread over to here.

    Quite an important debate and I'm sure we're all keen the thread gets refined/corrected so it's a proper reference

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    Its a very interesting thread indeed.

    I have used CDS tubing for the cage in my quattro. I spoke to the guy at Elmdon Metals when I was ordering it, T45 was hugely expensive and he told me I would have to get the minimum spec tubing as per blue book. So it would have been far stronger but no lighter. He advised me that the 50X2mm tube was lighter than the 45X2.5 so thats what I went for, it does however look very big in the car.

    So the question is how are some people getting away with using T45 tube of thinner diameter and thickness in one off cages? For some reason I had always thought that the main 6 point cage as drawn in the blue book must be minimum thickness. However if you are adding more optional bars as drawn in the blue book therefore strengthening the cage no matter what thickness you use? In that situation I am unsure as to what you can use as you so often see bars like door bars made from 40mm tubing etc?

    Here is a build thread to somebody who built a spaceframed chasis/ roll cage and after sending him a pm he replied that the main structure was 2mm and .9 on the rest. The car has competed widely winning the scottish saloon car championship and has won it at least once.

    http://passionford.com/forum/restora...-eat-dust.html

    So is it a case of the scrutineering not doing there job or something else?
    Last edited by Hamish; 5th December 2009 at 16:22.

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    Quote Originally Posted by Hamish
    50X2mm tube was lighter than the 45X2.5 so thats what I went for, it does however look very big in the car.
    Agree - 50mm stands out a mile.

    Quote Originally Posted by Hamish
    So the question is how are some people getting away with using T45 tube of thinner diameter and thickness in one off cages?
    Some non-race cars, ie track cars, are being supplied with T45 at the (paying) customer's request. I believe the cage suppliers can supply whatever's asked of them, because the gatekeepers are the MSA Scrutineers.

    Quote Originally Posted by Hamish
    For some reason I had always thought that the main 6 point cage as drawn in the blue book must be minimum thickness. However if you are adding more optional bars as drawn in the blue book therefore strengthening the cage no matter what thickness you use? In that situation I am unsure as to what you can use as you so often see bars like door bars made from 40mm tubing etc?
    /reaches for Blue Book

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    Some more info found here:

    http://www.customcages.co.uk/roll-cages/certification

    Quote Originally Posted by Custom Cages
    To compete in any race or rally your roll cage will need to comply with either MSA or FIA regulations. (Effectively, the MSA is governed by the FIA so if a roll cage design complies with FIA regs, then it is also eligible for MSA events). There are some instances where the FIA allow certain design features where the MSA do not (and vice versa).
    Quote Originally Posted by Custom Cages
    The certification process generally allows for a lighter roll cage because it is a bespoke design where the diameter and thickness of each tube is optimised to achieve the overall strength required by the FIA/MSA rules.

    In order to compete in MSA/FIA events every vehicle, which has a certificated design of roll cage, should have a copy of a valid certificate to present at scrutineering. Custom Cages has certified the majority of popular roll cages. All other roll cages < ie those not certificated > comply with MSA/FIA regulations and receive a Letter of Conformity for competitors to present to scrutineers.
    Also some info on Safety Devices' site here

    I think the the SD page is irrelevant through, because it's all about International Competition, pre and post 1 Jan 2003 (I think the first date is a typo).

    As regards T45 use, it then comes back to what's in article 253 (link in post 1) / or the Blue Book equivalent (ie the first Custom Cages para above).

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    From post 1:

    Quote Originally Posted by MSA Blue Book 2011, Section K, p156

    27. Minimum CDS tube specifications are:

    Minimum Material: Cold Drawn Seamless Carbon Steel
    Minimum Yield Strength: 350 N/mm2
    • Minimum Dimensions (Ø mm):
    • 45x2.5 or 50x2.0
    • 38x2.5 or 40x2.0 (for roll cages/bars approved prior to 1995)


    Hmmm, 'Minimum'. That's got to be where the answer lies. If T45 is deemed to be above the threshold of the minimum 'material' & 'yield strength', then logically it should be ok? Provided it meets the minimum dia and tube thicknesses given?

    So T45 used in cages not FIA certificated / not given a Letter of Conformity suffers a weight disadvantage, agaist thinner tube used in FIA/Conformity cages?

    So it'll gain the 0.5 kg per metre of tubing (or 10 - 15%) T45 weight saving over CDS which pascal quoted in his Audi thread, but there's no scope to lighten any further through thinner tube?

    I've just checked 1992 and 1997 MSA Blue Books and this text hasn't essentially changed since then.
    Last edited by Chris Eyre; 3rd June 2011 at 12:16. Reason: MSA reference updated

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    An interesting question would be who has ever had there cage tubing drilled by the scrutineers?

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    From post 1

    Quote Originally Posted by Chris Eyre
    Where a cage is uncertificated, the MSA require an 6mm hole to be drilled into a part of the cage (often the screenrail) where the tube thickness can be quickly seen by a scrutineer, to establish the correct thickness.
    Just dug out:
    Quote Originally Posted by MSA Blue Book 2009, Section C(c), p156

    39. An effective rollbar must be fitted with its top edge not less than 5cm above the helmet of the normally seated Driver. It must be wider than the Driver’s shoulders at that height. It must be constructed of good quality seamless steel tubing of minimum 35mm
    diameter and wall thickness of 2mm. It should have a 6mm hole drilled in the underside for checking the tube thickness. It should have the top bar straight or slightly curved but no tubes meeting in an inverted ‘V’. It must be effectively braced to structural members.

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